(x+3)²=17x+21 expand first x²+6x+9=17x+21 minus 17x+21 both sides x²-11x-12=0 we can easily factor what 2 numbers multiply to get -12 and addd to get -11? -12 and 1 (x-12)(x+1)=0 x-12=0 x=12
x+1=0 x=-1
x=-1 and 12 you can use either method, I would use factoring
